Fixed in spacewalk.git in commit 6da41679b8fe50538f108111fabe5b5cfc46e636

Cherry-picked to satellite.git as commit 59dc7942b76e37540a4ba7652a9e076f95d0ca59

I am facing  this problem agter updating to 

rhn-check-1.0.0-57.el6.noarch
rhn-client-tools-1.0.0-57.el6.noarch
rhn-setup-1.0.0-57.el6.noarch
rhn-setup-gnome-1.0.0-57.el6.noarch
yum-rhn-plugin-0.9.1-20.el6.noarch

I have checked this is not an issue now with:

yum-3.2.29-17.el6.noarch
yum-rhn-plugin-0.9.1-26.el6_1.1.noarch

This was a regression caused during development. Customers could not see it as the buggy package was newer released:

# grep serverURL= /etc/sysconfig/rhn/up2date 
serverURL=https://xmlrpc.rhn.redhat.com/XMLRPC
# rpm -q yum yum-rhn-plugin
yum-3.2.27-14.el6.noarch
yum-rhn-plugin-0.9.1-5.el6.noarch
# mv /etc/sysconfig/rhn/systemid{,.OK}
# yum repolist
 => PASS

Updated yum\* to what is on Prod:

# rpm -q yum yum-rhn-plugin
yum-3.2.27-14.el6_0.1.noarch
yum-rhn-plugin-0.9.1-7.el6.noarch
# mv /etc/sysconfig/rhn/systemid{,.OK}
# yum repolist
 => PASS

=> Will close as CURRENTRELEASE once RHEL6.1 is out.

An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHBA-2011-0565.html